// prime 算法
#include<bits/stdc++.h>
using namespace std;

const int N = 510, INF = 0x3f3f3f3f;

int n, m;
int g[N][N];
int dist[N];
bool st[N];

int prim() {
    memset(dist, 0x3f, sizeof dist);

    int res = 0;
    
    for (int i = 0; i < n; i++) {
        int t = -1;
        for (int j = 1; j <= n; j++) {
            if (!st[j] && (t == -1 || dist[t] > dist[j])) t = j;
        }

        if (i != 0 && dist[t] == INF) return INF;
        if (i != 0) res += dist[t];

        for (int j = 1; j <= n; j++) dist[j] = min(dist[j], g[t][j]);
        st[t] = true;
    }
    return res;
}

int main() {
    scanf("%d%d", &n, &m);

    memset(g, 0x3f, sizeof g);

    while (m -- ) {
        int a, b, c;
        scanf("%d%d%d", &a, &b, &c);
        g[a][b] = g[b][a] = min(g[a][b], c);
    }

    int t = prim();

    if (t == INF) puts("impossible");
    else cout << t << endl;

    return 0;
}